What is the law of conservation of mass?

The law of conservation of mass states that mass can neither be created nor destroyed in a chemical reaction. This means that the total mass of the reactants is always equal to the total mass of the products.

The law was proposed by the French scientist Antoine Lavoisier.

Example:
If 10 g of hydrogen reacts with 80 g of oxygen to form water, the total mass of water produced will be 90 g.

In simple terms, matter does not disappear or appear during a chemical reaction—it only changes from one form to another.